Production Process of a Clad Material
A reed frame for an integrated circuit may be usually fabricated by press working a strip like material W shown in FIG. 26. Those portions of the reed frame which will be used later as bonding sections need to be coated with a metal, such as Al or Ag, for improving adhesivity. For this reason, metal foils S, such as Al or Ag foils, are clad on those portions of the strip-like material W which will be used later as the bonding sections. This material is known as a partially or spot clad material, and, as the methods for producing such spot clad material, methods of "vacuum deposition", "plating" and "rolling-pressure contacting" have hitherto been used.
The method of "vacuum deposition" is however inconvenient in that a costly equipment is necessitated, those portions that are not coated by vacuum deposition need to be masked, and a relatively long time is involved in the operation of vacuum deposition. Namely, productive efficiency is lowered.
The "plating" method is also inconvenient in that certain species of metal to be clad cannot be formed by plating and a limit is imposed on the thickness of the metal layer produced efficiently by plating. Namely, it lacks general applicability.
The "rolling and pressure contacting" method consists in depositing an Al or Ag foil as a stripe on a strip-like reed frame material and mechanically or chemically eliminating unnecessary portions, so that spots of a desired shape will be left, as shown for example in JP Patent KOKAI Publication No. 59-1078 (1984). This method also is not satisfactory in that the yield of metal deposition is low, and an equipment is necessitated for eliminating unnecessary portions by masking. Namely, it causes elevated production costs.
Although the JP Patent KOKAI Publication 60- 227456 (1985) teaches a reed frame which may be produced by spot welding an Al foil on a reed frame material and processing the resulting assembly for cladding, this method has not been practically used because of the lack of an appropriate method for positioning and tacking the metal foil at a predetermined pitch. That is, although metal foil pieces of a predetermined length may be applied in position on a sheet material of a predetermined length and processed by pressure contacting and rolling to produce a spot-like or partial clad material of a predetermined length, the clad material can not be produced industrially.
It is an object of the present invention to provide a method and an apparatus for producing a clad material whereby metal foils of a predetermined size may be superimposed on a strip-like material at a constant pitch to enable mass production of a spot or partial clad material with higher accuracy.